1. Field of the Invention
The present invention relates generally to freight distribution systems, and in particular an intermodal transportation system utilizing flat railcars and local hybrid vehicle delivery of trailers and container-on-chassis trailers.
2. Description of the Related Art
Intermodal transportation of freight consists of the movement of individual freight containers utilizing different modes of transportation. The advantage of this method consists of increased efficiency in transportation of freight. Efficiencies are manifested in both the physical movement of the freight containers, and economical savings of bulk transportation of freight. As such, numerous approaches have been taken to maximize the physical and economic efficiencies of intermodal transportation. In particular, movement of freight utilizing a combination of railroad cars and tractor-trailers and container-on-chassis trailers suitable for travel on interstate highways has been the focus of much attention.
Two basic methods of moving freight by both railway and roadway consist of using either a semi-trailer and railroad flatcar combination, or a semi-trailer and bogie combination. A trailer and flatcar combination consists of a trailer having a kingpin positioned piggyback-style on the top of a conventional flatcar. The trailer is positioned on the flatcar at a transition point utilizing either handling equipment (e.g., saddle or swing crane, or forklift) or driven onto the railroad car using a ramp and tractor. Once positioned on the flatcar, the kingpin of the trailer is typically secured to a coupling device having a fifth wheel for securely engaging the trailer to the flatcar. Multiple flatcars can be assembled into a train for efficient movement of freight. An advantage of using a flatcar for transporting a trailer permits the compression and tension forces encountered during train movement to be transferred through the flatcar. Moreover, many variations of trailers can be transported using this method of moving freight, and the conventional flatcar can be assembled into a train for transportation along conventional railway routes.
Currently, loading of flatcars with handling equipment requires decoupling of the trailer from the tractor, engagement and disengagement of the handling equipment during the transition period, and secure engagement of the trailer with the flatcar. The steps are completed in reverse for unloading the flatcar. This process is time consuming and requires expensive and complex handling equipment at each transition point. Moreover, the trailers and freight can become damaged during the transition due to collisions, dropping, and the shifting of freight. Loading trailers onto flatcars utilizing ramps positioned at the end or alongside the flatcar allow the tractor-trailer to drive up and onto the flatcar for deposition of the trailer. This method is accomplished by either driving the tractor-trailer onto the flatcar tractor first, or by backing the tractor-trailer onto the flatcar trailer first. Because each trailer is typically secured by its kingpin to the flatcar, trailers can only be loaded one at a time in a circus-loading fashion. Although driving the trailer onto the flatcar avoids the hazards of using handling equipment to move the trailer, the circus-loading process is time consuming resulting in decreased efficiency during physical movement of the freight.
A trailer and bogie combination consists of a modified semi-trailer adapted for engaging a specialized railway bogie. A trailer used in this approach differs from that employed above because instead of a conventional flatcar handling the rail compression and tension forces, a trailer with structural enhancements, and modified undercarriage manages the forces of the train. Here, assembly of a railroad car consists of a conventional tractor first engaging the frame of the aft portion of the trailer with a suitable railway bogie. Upon disengagement of the tractor from the trailer, the fore portion of the trailer is engaged with a suitable railway bogie by either its kingpin or the frame. Additional equipment necessary for assembly of this type of railroad car typically consists of ramps, or assist mechanisms built into the enhanced trailer. This method of moving freight is economically attractive because the elimination of a conventional flatcar from the railroad car assembly decreases the overall weight of the individual railroad car thereby decreasing the weight the locomotive needs to move. However, the disadvantages of this method of freight transportation over the conventional flatcar method relate to the weight of the trailer associated with its structural enhancements. Because such trailers typically have more steel in them to handle forces encountered during train movement, and sometimes have components enabling the trailer to travel on both the roadway or railway, the higher tare weight of the trailer limits the amount of weight the trailer is permitted to transport over a roadway. Moreover, such railroad cars typically require dedicated rail service because they are not compatible with other rail traffic due to their unique composition, and inability of the bogie couplings to manage usual train forces.
Heretofore there has not been available an inter-modal transportation system with the advantages and features of the present invention.